Increased Endotoxin Activity in COVID-19 Patients Admitted to the Intensive Care Unit.

OBJECTIVE: Endotoxin is a component of Gram-negative bacteria and can be measured in blood using the endotoxin activity assay (EAA). Endotoxin exposure initiates an inflammatory cascade that may contribute to organ dysfunction. Endotoxemia has been reported in previous viral pandemics and we investigated the extent of endotoxemia and its relationship to outcomes in critically ill patients with COVID-19. MATERIALS AND METHODS: We conducted a Prospective Cohort Study of 96 critically-ill COVID-19 patients admitted to the George Washington University Hospital ICU from 25 Mar-6 Jun 2020. EAA and inflammatory markers (ferritin, d dimer, IL-6, CRP) were measured on ICU admission and at the discretion of the clinical team. Clinical outcomes (mortality, LOS, need for renal replacement therapy (RRT), intubation) were measured. Statistical analysis was conducted using descriptive statistics and effect estimates with 95% confidence intervals. Comparisons were made using chi-square tests for categorical variables, and T-tests for continuous variables. RESULTS: A majority of patients (68.8%) had high EAA [≥ 0.60], levels seen in septic shock. Only 3 patients had positive bacterial cultures. EAA levels did not correlate with mortality, higher levels were associated with greater organ failure (cardiovascular, renal) and longer ICU LOS. Among 14 patients receiving RRT for severe AKI, one had EAA < 0.6 (p = 0.043). EAA levels did not directly correlate with other inflammatory markers. CONCLUSIONS: High levels of endotoxin activity were found in a majority of critically-ill COVID-19 patients admitted to the ICU and were associated with greater risk for cardiovascular and renal failure. Further investigation is needed to determine if endotoxin reducing strategies are useful in treating severe COVID-19 infection.

RNA Sequencing in COVID-19 patients identifies neutrophil activation biomarkers as a promising diagnostic platform for infections.

Infection with the SARS-CoV2 virus can vary from asymptomatic, or flu-like with moderate disease, up to critically severe. Severe disease, termed COVID-19, involves acute respiratory deterioration that is frequently fatal. To understand the highly variable presentation, and identify biomarkers for disease severity, blood RNA from COVID-19 patient in an intensive care unit was analyzed by whole transcriptome RNA sequencing. Both SARS-CoV2 infection and the severity of COVID-19 syndrome were associated with up to 25-fold increased expression of neutrophil-related transcripts, such as neutrophil defensin 1 (DEFA1), and 3-5-fold reductions in T cell related transcripts such as the T cell receptor (TCR). The DEFA1 RNA level detected SARS-CoV2 viremia with 95.5% sensitivity, when viremia was measured by ddPCR of whole blood RNA. Purified CD15+ neutrophils from COVID-19 patients were increased in abundance and showed striking increases in nuclear DNA staining by DAPI. Concurrently, they showed >10-fold higher elastase activity than normal controls, and correcting for their increased abundance, still showed 5-fold higher elastase activity per cell. Despite higher CD15+ neutrophil elastase activity, elastase activity was extremely low in plasma from the same patients. Collectively, the data supports the model that increased neutrophil and decreased T cell activity is associated with increased COVID-19 severity, and suggests that blood DEFA1 RNA levels and neutrophil elastase activity, both involved in neutrophil extracellular traps (NETs), may be informative biomarkers of host immune activity after viral infection.